Deletion of the propeptide from human preproapolipoprotein A-II redirects cotranslational processing by signal peptidase.

摘要: The functions of NH2-terminal propeptides are not known. We have used apoA-II as a model to study prosegment structure/function relationships. primary translation product human apolipoprotein A-II mRNA contains an 18-amino acid signal peptide, 5-amino propeptide, and the mature 77-amino plasma protein sequence. Its propeptide was deleted by site-directed mutagenesis cloned cDNA. effects this mutation on cotranslational translocation proteolytic processing were assessed using in vitro transcription/translation/microsomal membrane system. Deletion did affect translocation. However, without its peptidase cleavage redirected different site located between 2nd 3rd residues protein. Since structure peptide altered mutant, these results suggest that sequences downstream from (e.g. propeptides) may modulate, or participate defining, correct processing.